Thermionic translating device.



A. McL. NICOLS'ON.

THERMIONIC TRANSLATING DEVICE.

APPLICATION r1150 APR. 19, 1915.

Patented Jan. 25, 1916.

//7 1 61) for i NDER McLEAN NICOLSON, OF NEW YORK, N. Y., ASSIGNOR, BYMESNE ASSIGN- MENTS, T0 WESTERN ELECTRIC COMPANY, INCORPORATED, ACORPORATION OF NEW YORK.

Specification of Letters Patent.

THEONIC TBANSLATIN G DEVICE Patented Jain. 25, 1916.

Application filed Apr1l19, 1915, Serial No. 22,306.

ments in Thermionic Translating-Devices,

of which the following is a full, clear, concise, and exact description.

This invention relates to thermionic translating devices and inparticular to vacuum tube devices in which the cathode element is heatedby radiation from an adjacent heatin element, and its object is toproduce a large current output with a. minimum number of electrodeelements.

In a copending application I have described a form of so-calledequi-potential cathode element forv use in a thermionic translatingdevice, which element comprises a tube of quartz or similar material,the outer surface of which is 'ven a thermionically active coating,which is brought to incandescen'ce by means of an electrically heatedresistance element located inside of the tube but the external outing.-The present invention contemplates the employment of this resistance orheating element as the input electrode of a translating device, and. isbased on my discovery that the input electrode may be heated toincandescence Without interfering with the operation of such Figure 1 ISa device of the audion type employing the cathode and input elementarrangement of this invention, and Fig. 2 illustrates diagrammaticallyhow. the various electrodes of such a device may be connected into atypicalcircuit arrangement for the modification of telephonic or othercurrents.

In Fig. 1, 3 is an evacuated vessel, containing anodes or plates 4, anda plural ty of quartz tubes'5 the outer surfaces of which havethermionicall active coatings 6. A platinum spiral 7- is threadedthrough the tubes 5 iii-succession, as shown, and terminates on the twoleading-m wires 8; The

' coating 6 is prepared as described in my copcnding application byapplying a layer of platinum tetra-chlorid to the outut of electricalcontact with side of the tubes 5 and baking. This produces a platinumdeposit which in turn is coated by a mixture of the oxids of strontiumand barium or other suitable thermionically active material. Leading-inwires 9 may be conveniently attached to the coating 6 b wrapping one endof the wire 9 about sai coating as shown at 10 and covering the jointthus formed with platinum tetrachlorid and baking. By connecting all ofleading-in wires 9 to one terminal 11, the surface 6 may be made tofunction as a single cathode surface of large electron-emittingarea,.all parts of which surface can be maintained at the same potentialwith respect to the anodes 4. Such a cathode is therefore what may becalled an equi-potential cathode as distinguished from the-distributedpotential cathode of the filamentary type customarily employed in audiondevices.

In adapting such a device to use as an amplifier of telephonic currents,the terminels 8 of the platinum spiral 7 are connected to terminals ofthe battery 12 whose function it is to heat the spiral 7 toincandescence. The heating of this spiral causes a consequentincandescing of the cathode surfaces 6, making them thermionicallyactive. In the diagrammatic arrangement ofFig. 2 one terminal 8 of thespiral 7 is connected to the secondary winding 13 of an inputtransformer 14 and serves therefore as an frequency characteristicsasthe '1" ut currentimpressed on'the'winding13. t is thus seen that thearrangement. described r0 vides a thermionic translating device a ingthe advantages of. an" 'equi-potential cathode with only three electrodeelements, and without the necessityof cm loyin an additionalheating'element for t e cat ode surface. Inasmuch as the heating elementemployed is used also as an input element and is not located between thecathode surface made thermionically active by heat radiation from saidinput electrode.

'2. In a thermionic translating device, a thermionically active cathodesurface and a heated electrode adjacent said surface and serving thedouble purpose of an input electrode and a heater for said surface.

3. A thermionic translating device comprising an evacuated vessel, acathode and an input electrode within said vessel and means outside.said vessel for incandescing said in'put'electrode.

4. A thermionic translating device comprising an evacuated vessel, anequi-potential cathode within said vessel, an input electrode alsowithin said vessel and in close proximity to said cathode, and meansoutside said vessel for heating said input electrode and therebyrendering said cathode tllermionically active.

In witness whereof, I hereunto subscribe my name this 16th day of April,A. D. 1915.

ALEXANDER MOLEAN NICOLSON.

